I shot some surfing this weekend, just trying to get the hang of the 5D3. Servo mode is amazing with the expanded points. Because the motion is so erratic, I usually get about 40-50% in very good focus. With the 5D3, that jumped to 90%. It was hard to find shots that weren't in focus.
Right after, I swapped to one-shot to take a picture of the wife, and like some others here the focus confirmation seemed slow. There was plenty of light, it just took an extra second for the confirmation to flash. I was expecting pretty much immediate focus so I accidentally took a shot before confirmation, then took another right after to make sure I had a good image. What was interesting is the focus on the two images was practically identical, I couldn't tell them apart.
I did have point expansion on and used the points on the left hand side of the frame for both images. I'm wondering if maybe the shot does focus quickly, but the confirmation is lagging behind. Or perhaps the central point you choose focuses quickly, but the AF system takes a little time to check the surrounding points to make sure everything is fine and dandy before giving confirmation. I'll try with expansion off later and see if anything comes of it.